Despite significant advances made in reducing gay men's involvement in HIV risk-related sexual behaviors and the incidence of new infection in this population, there has been little progress made in reducing young gay men's risk for HIV infection. Prevention efforts have in part failed because significant gaps exist in our understanding of the broad array of individual, familial, social, and community characteristics that both individually and collectively influence young men who have sex with men (YMSM) to engage in both risk and protective factors. Building on our own research with YMSM and other high risk youth groups, Children's Hospital Los Angeles (CHLA) is proposing to conduct theory-driven (i.e., the social ecological model) ethnographic and epidemiologic research to examine YMSM's drug use patterns, involvement in HIV sexual risk and protective behaviors, and health promoting and seeking behaviors in the context of individual experiences (e.g., sexual identity and coming-out experience) and the family (e.g., family composition and environment, familial/parental support), which in turn will be examined in the context of the youth's interpersonal relationships(e.g., number and nature of intimate relationships, peer ties and integration, peer support), and community contexts(e.g., academic engagement, support from educators and other members from the community in which they live and/or spend time, integration within the gay community and linkage with and use of gay social services, including HIV prevention and health promoting services). The proposed study will involve three phases of research. During Phase 1, formative ethnographic research will be conducted to characterize and contextualize the constructs of interest and the proposed relationship between these constructs and the proposed dependent or outcome variables, and develop and/or adapt existing survey instruments that are appropriate for use with the target population. During Phase 2, epidemiological research will be conducted by administering a structured survey to 535 YMSM, ages 18 to 24, who will be racially diverse and recruited using a venue-based sampling design; ethnographic research will be conducted with a subset of 100 of these youth. During Phase 3, the study findings will be summarized and widely disseminated to researchers; federal, state and local policy makers; service providers; advocacy groups; and community organizations that are working with YMSM.